This application relates to a turbine exhaust case.
Gas turbine engines typically include a fan delivering air into a bypass duct as propulsion air. Air also passes into a core engine and to a compressor. The air in the compressor is compressed and delivered into a combustor where it is mixed with fuel and ignited. Products of this combustion pass downstream over turbine rotors, driving them to rotate.
Historically, a fan drive turbine drove the fan and a low pressure compressor at a single speed. More recently, a gear reduction has been placed between the fan drive turbine and the fan.
With this change, the fan may rotate at slower speeds than the fan drive turbine and the low pressure compressor. This allows the diameter of the fan to increase and has resulted in an increase in the amount of air delivered into the bypass duct compared to the air delivered into the core engine. A quantity known as the bypass ratio compares the volume of air delivered into the bypass duct to the volume of air delivered into the compressor. Bypass ratios have increased with modern gas turbine engine utilizing a fan drive gear reduction.
As the bypass ratio increases, there is less cooling air for cooling internal components, such as a turbine exhaust case.